As shown in FIG. 19, for example, it is desirable to reduce the gap between a wheel arch 2 of an automobile vehicle body 1 and a tire 3, and to keep a space in a wheel house. To meet these demands, as shown FIG. 20, it has been the practice in the art to bend a flange 5 comprising a welded joint of an inner panel 4a and an outer panel 4b of the vehicle body 1, into the vehicle body 1.
According to a hem machining apparatus disclosed in Patent Document 1, for example, as shown in FIG. 21, a workpiece W in the form of an automobile body side is conveyed along a production line 6, and hem dies 7a through 7f, three in each of two locations, corresponding to various body sides are disposed on one side of the production line 6. A die feed robot 8 is disposed between the hem dies 7a through 7c and the hem dies 7d through 7f. The die feed robot 8 selectively holds either one of the hem dies 7a through 7f for the workpiece W, and machines the workpiece W with the selected hem die.
As shown in FIG. 22, the hem die 7a, for example, is removably held by a hand changer 10 on the distal end of a wrist 9 of the die feed robot 8. The hem die 7a has a pair of holding brackets 11 with a workpiece holder 12 on upper portions thereof. A prebending tool 13 is angularly movably supported by a support shaft 14 in the vicinity of the workpiece holder 12. The prebending tool 13 has a tip end for prebending a flange F of the workpiece W.
A bending tool 15 is angularly movably mounted on the holding brackets 11 by a support shaft 16. The bending tool 15 and the prebending tool 13 are coupled to each other by a joint 17. An actuating cylinder 19 is angularly movably supported on the holding brackets 11 by a support shaft 18, and has a piston rod 19a having a distal end on which the bending tool 15 is angularly movably supported.
As shown in FIG. 23A, an apparatus 120 for bending a wheel house as disclosed in Patent Document 2 has a workpiece holder 122 mounted on a frame 121 and a workpiece pusher 124 and a workpiece bender 123 which are slidably mounted on the frame 121.
The workpiece holder 122 is set on an inner corner of a flange 126 of a wheel arch 125. As shown in FIG. 23B, the workpiece pusher 124 is slid in the direction indicated by the arrow 1, and pushes the flange 126 against the workpiece holder 122. Then, as shown in FIG. 23C, the workpiece bender 123 is slid in the direction indicated by the arrow 2 until it abuts against the flange 126. As shown in FIG. 23D, the workpiece bender 123 is further slid in the direction indicated by the arrow 3, bending the flange 126.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2000-312935
Patent Document 2: Japanese Laid-Open Patent Publication No. 9-108743